Asphaltic roofing membranes are often employed to cover flat or low sloped roofs. These membranes are typically installed by unrolling a roll of material on a roof surface and then heat seaming adjacent membranes together to form an impervious water barrier on the roof surface.
As part of the manufacturing process, the asphaltic roofing membranes are often coated with granular material. Among the benefits associated with the use of these granules is the ability to reflect solar radiation, thereby maintaining a cooler roof surface, protect the asphalt compounds by blocking the sunlight and UV rays, provide a desired color for cosmetic purposes and provide a small degree of fire resistance. In addition, the granules protect the asphaltic roofing membrane from natural elements such as precipitation and from foot traffic across the roof. Current production methods often utilize gravity by dropping the granules from a hopper onto a tacky asphaltic sheet where the granules are adhered.
Current manufacturing methods for asphaltic articles suffer from a number of disadvantages. For example, it is difficult to obtain an even, consistent, and thorough coverage of the granules over the asphaltic sheet. Even in those manufacturing methods employing various stages of granule application, the desired coverage of the asphaltic sheet is rarely obtained. Consistent and thorough granule coverage is particularly important to highly reflective asphaltic articles, since uncovered portions of the article provide significantly reduced reflectivity.
Thus, there is a need for an improved method of manufacturing asphaltic articles that have a more even, consistent and/or thorough coverage of a granule coating.